Fixing plate, optical device and projector

ABSTRACT

The invention provides a fixing plate, optical device and projector capable of preventing against color unevenness occurrence and pixel deviation. Specifically, in each of the four sides of a luminous-flux exit surface of a plate part of a fixing plate, there can alternately be formed a first cutout in a groove form extending from an opening toward an outer edge of the plate part and nearly orthogonal to a lengthwise of each side, and a second cutout in a groove form extending from the outer edge toward the opening and nearly orthogonal to the lengthwise of each side.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a fixing plate, optical device andprojector.

2. Description of Related Art

Conventionally, there is known so-called a three-plate type projectorwhich is provided with a light source, a color-separating optical systemfor separating the luminous flux emitted from the light source intothree colors of light of R, G and B by use of a dichroic mirror, threelight modulator devices for modulating the separated luminous fluxesbased on each color of light in accordance with image information, and acolor synthesizer device for synthesizing the luminous fluxes modulatedby the color modulator devices.

Such a projector light modulator device has a light modulator elementfilled with a light modulator element proper between a pair ofsubstrates, and a holder frame holding the light modulator element. Theholder frame of the light modulator device is attached on the fixingplate. By fixing the fixing plate onto a luminous-flux incident end faceof a color-synthesizing optical device, the light modulator device andthe color-synthesizing optical device are integrated together. See, forexample, Publication of JP-A-2000-259094 (page 6, FIG. 5).

SUMMARY OF THE INVENTION

In such a projector, in the case there is a difference between theexpansion coefficient of the holder frame of the light modulator deviceand the expansion coefficient of the fixing plate, the holder frame isapplied by a deformation force of expansion/contraction ratio of thefixing plate. This deforms the gap between the substrates in pair of thelight modulator device to thereby change the transmittance oftransmission luminous flux, possibly causing color unevenness in theprojection image.

Meanwhile, usually, the fixing plate fixing the light modulator deviceis made of metal whereas the color-synthesizing optical device on whichthe fixing plate is to be bonded is made of glass. Thus, the expansioncoefficients are greatly different. The fixing plate is to be deformedby a force caused by the difference of expansion/contraction ratio, topossibly deviate the fixing plate relative in position to thecolor-synthesizing optical device. The fixing plate if deviated inposition relative to the color-synthesizing optical device results in apositional deviation of the color-synthesizing optical device fixed onthe fixing plate, possibly causing a pixel deviation in the projectionimage.

It is an object of the present invention to provide a fixing plate,optical device and projector capable of preventing against colorunevenness occurrence and pixel deviation.

A fixing plate of the invention is a fixing plate attached at aluminous-flux exit side of a light modulator device for modulating aluminous flux emitted from a light source in accordance with imageinformation and forming an optical image, and for fixing the lightmodulator device on a color-synthesizing optical device for synthesizingcolors of light exited from the light modulator device. The fixing platecan include a plate part in a rectangular plate form fixing the lightmodulator device and formed with an opening for transmitting a luminousflux exited from the light modulator device. In four sides of aluminous-flux incident surface or luminous-flux exit surface of theplate part, a groove-formed cutout is formed extending nearly orthogonalto a lengthwise of each side.

According to the invention like this, a cutout in a groove form isformed extending nearly orthogonal to a lengthwise of each side, in foursides of the luminous-flux incident surface or luminous-flux exitsurface of the plate part of the fixing plate, hence making it possibleto suppress the plate part of the fixing plate fromexpanding/contracting. This can prevent the light modulator device frombeing applied by a deformation force of expansion/contraction of thefixing plate, making it possible to prevent a transmittance change oftransmitting luminous flux through the light modulator device andfurther an occurrence of color unevenness.

Meanwhile, because the fixing plate can be suppressed fromexpanding/contracting, the expansion/contraction ratio of the fixingplate can be approximated to the expansion/contraction ratio of thecolor-synthesizing optical device, making it possible to decrease theforce caused by a difference in expansion/contraction ratio.Consequently, it is possible to prevent the fixing plate from deviatingin position relative to the color-synthesizing optical device, andfurther the light modulator device fixed on the fixing plate fromdeviating in position. In this manner, because the light modulatordevice can be prevented from deviating in position, pixel deviation canbe prevented in the projection image.

In the invention, preferably the cutout has a first cutout partextending from the opening toward an outer edge and a second cutout partextending from the outer edge toward the opening, the first cutout partand the second cutout part being alternately formed in each side.According to the invention, because there are alternately formed, ineach side, the first cutout part extending from the opening toward anouter edge and the second cutout part extending from the outer edgetoward the opening, a warp can be prevented from occurring uponexpansion/contraction of the fixing plate.

Furthermore, in the invention, preferably the number of the cutouts isthe value resulting when an expansion coefficient of the fixing plate isdivided by an expansion coefficient of the color-synthesizing opticaldevice and then is changed into an integer, or the above value changedinto an integer is multiplied by an integer. By providing the numbermentioned above as the number of cutouts, it is possible to decrease thedifference between the expansion/contraction ratio of the fixing plateand the expansion/contraction ratio of the color-synthesizing opticaldevice. This makes it possible to prevent a positional deviation of thefixing plate relative to the color-synthesizing optical device andfurther a positional deviation of the light modulator device fixed onthe fixing plate. In this manner, because the light modulator device canbe prevented from deviating in position, pixel deviation can be alsoprevented in the projection image.

Furthermore, in the invention, preferably the expansion coefficient is7.0×10⁻⁶ or greater and 26×10⁻⁶ or smaller. Particularly, it ispreferably a value nearly intermediate between the expansion coefficientof the holder frame of light modulator device fixed on the fixing plateand the expansion coefficient of the color-synthesizing optical device.

In this manner, by taking the value nearly intermediate between theexpansion coefficient of the holder frame and the expansion coefficientof the color-synthesizing optical device, the difference can be reducedbetween the expansion coefficient of the holder frame and the expansioncoefficient of the color-synthesizing optical device.

Namely, because of the reduced difference between the expansioncoefficient of the holder frame and the expansion coefficient of thecolor-synthesizing optical device, the holder frame can be preventedfrom being applied by a force caused by expansion/contraction of thefixing frame. This makes it possible to prevent against a transmittancechange of transmitting luminous flux through the light modulator deviceand further an occurrence of color variation.

Meanwhile, because of the reduced difference between the expansioncoefficient of the fixing plate and the expansion coefficient of thecolor-synthesizing optical device, it is possible to reduce the forceoccurring due to the difference in expansion/contraction ratio betweenthose. This can prevent a positional deviation of the fixing platerelative to the color-synthesizing optical device, and further canpositively prevent a pixel deviation occurring due to such a positionaldeviation.

An optical device of the invention is an optical device having a lightmodulator device for modulating a luminous flux emitted from a lightsource in accordance with image information and forming an opticalimage, and a color-synthesizing optical device for synthesizing colorsof light modulated by the light modulator device. The optical device caninclude a fixing plate for fixing the light modulator device at aluminous-flux incident end face of a color-synthesizing optical device,the fixing plate being a fixing plate according to any of the foregoingfixing plates. According to the invention like this, because of theprovision of any of the foregoing fixing plates, there is exhibited aneffect capable of preventing against color unevenness occurrence andpixel deviation occurrence.

Furthermore, a projector of the invention can include an optical devicementioned above and a projection optical system for projecting an imageformed by the optical device. According to the invention like this,because of the provision of the foregoing optical device, there isexhibited an effect similar to the optical device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numerals reference like elements, and wherein:

FIG. 1 is a perspective view of a projector in the this embodiment ofthe present invention as viewed from the upper front;

FIG. 2 is a perspective view of the projector as viewed from the lowerback;

FIG. 3 is a perspective view showing an interior of the projector;

FIG. 4 is a perspective view showing an interior of the projector;

FIG. 5 is an exploded perspective view showing an optical unitconstituting the projector;

FIG. 6 is a typical view showing the optical unit;

FIG. 7 is a perspective view showing an optical device main body;

FIG. 8 is an exploded perspective view showing the optical device mainbody;

FIG. 9 is a perspective view showing a fixing plate of the opticaldevice main body;

FIG. 10 is a perspective view showing a holder frame of the opticaldevice main body;

FIG. 11 is a perspective view of the holder frame as viewed in thedirection different from FIG. 10;

FIG. 12 is a plan view of the holder frame;

FIG. is 13 a sectional view showing an essential part of the holderframe;

FIG. 14 is a sectional view showing an essential part of the holderframe;

FIG. 15 is a plan view of the holder frame;

FIG. 16 is a sectional view showing an essential part of the holderframe; and

FIG. 17 is a sectional view showing an essential part of the holderframe.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereunder, an embodiment of the invention is explained based on thedrawings.

FIG. 1 is a perspective view of a projector 1 according to the inventionas viewed from the upper front. FIG. 2 is a perspective view of theprojector 1 as viewed from the lower back.

As shown in FIGS. 1 and 2, the projector 1 has an exterior case 2 nearlyin a cubic form formed by injection molding. The exterior case 2 is asynthetic resin housing accommodating the main body of the projector 1,with an upper case 21 and a lower case 22. These cases 21, 22 areconstructed removable from each other.

The upper case 21 is structurally includes an upper surface 21A, a sidesurface 21B, a front surface 21C and a back surface 21D respectivelyconfiguring an upper surface, a side surface, a front surface and backsurface of the projector 1, as shown in FIGS. 1 and 2.

Likewise, the lower case 22 also structurally includes a lower surface22A, a side surface 22B, a front surface 22C and back surface 22Drespectively configuring a lower surface, a side surface, a frontsurface and a back surface of the projector 1, as shown in FIGS. 1 and2.

Consequently, in the cubic exterior case 2, a cubic side part 210 isconfigured by connecting between the side surfaces 21B, 22B of the uppercase 21 and lower case 22 in a continuous fashion, as shown in FIGS. 1and 2. Similarly, a front part 220 is configured by connecting betweenthe front surfaces 21C, 22C, a back part 230 by connecting between theback surfaces 21D, 22D, an upper part 240 by the upper surface 21A, anda lower part 250 by the lower surface 22A, respectively.

As shown in FIG. 1, in the upper surface part 240, an operation panel 23is provided at the front thereof. A speaker hole 240A for outputtingsound is formed in the vicinity of the operation panel 23.

In the side part 210 on the right as viewed from the front, there isformed an aperture 211 bestriding the two side surfaces 21B, 22B. Here,a main board 51 and an interface board 52, referred later, are providedwithin the exterior case 2. Through an interface panel 53 attached onthe aperture 211, exposed outside are a connection 51B mounted on themain board 51 and a connection 52A mounted on the interfaced board 52.In these connections 51B, 52A, the projector 1 is connected withexternal electronic appliances, etc.

In the front part 220, a circular aperture 221 bestriding both the twofront surfaces 21C, 22C is formed on the right as viewed from the frontand in the vicinity of the operation panel 23.

In a manner corresponding to the aperture 221, a projection lens 46 isarranged within the exterior case 2. On this occasion, the projectionlens 46 at its tip is exposed outside out of the aperture 221. Through alever 46A as a part of the exposed part, the projection lens 46 can befocus-operated manually.

In the front part 220, an air exit port 222 is formed in a positionopposite to the aperture 221. The air exit port 222 is formed with asafety cover 222A.

As shown in FIG. 2, in the back part 230, a rectangular aperture 231 isformed at the right as viewed from the back surface so that an inletconnector 24 is exposed out of the aperture 231.

In the lower part 250, a rectangular aperture 251 is formed in a centerat a right end as viewed from the below. On the aperture 251, a lampcover 25 is removably provided covering the aperture 251. By removingthe cover 25, a light source lamp, not shown, can be exchanged easily.

Meanwhile, in the lower part 250, a rectangular surface 252 recessed onestep inward is formed at the left as viewed from the below and in thecorner close to the back surface. In the rectangular surface 252, an airintake port 252A is formed to intake cooling air from the outside. Therectangular surface 252 is removably provided with an air intake cover26 covering the rectangular surface 252. The air intake cover 26 isformed with an aperture 26A corresponding to the air intake port 252A.On the aperture 26A, an air filter, not shown, is provided to preventdust from intruding into the interior.

Furthermore, in the lower part 250, a rear leg 2R structuring a leg ofthe projector 1 is formed nearly in a rear center. Meanwhile, front legs2F similarly configuring the legs of the projector 1 are respectivelyformed in the front left and right corners in the lower surface 22A.Namely, the projector 1 is supported at three points by the rear leg 2Rand the two front legs 2F.

The two legs 2F are each structured to advance and retract vertically sothat they can adjust the inclination (position) of the projector 1 indirections of front, back and left and right, thereby enablingpositional adjustment for a projection image.

Meanwhile, as shown in FIGS. 1 and 2, a recess 253 in a cubic form isformed nearly in the front center in the exterior case 2, in a mannerbestriding the lower part 250 and the front part 220. The recess 253 isprovided with a cover member 27 slidable back and forth and covering thelower and front region of the recess 253. By the cover member 27, therecess 253 accommodates therein a remote controller (remocon), notshown, for remotely operating the projector 1.

Here, FIGS. 3 and 4 are perspective views showing the interior of theprojector 1. Specifically, FIG. 3 is a view that the upper case 21 ofthe projector 1 is removed from the state of FIG. 1. FIG. 4 is a viewthat the control board 5 is removed from the state of FIG. 3.

The exterior case 2, as shown in FIGS. 3, 4, is provided with a powersupply unit 3 arranged along the back part and extending in left andright directions, an optical unit 4 as an optical system arranged infront of the power supply unit 3 and nearly in an L-form as viewed inplan, and a control board 5 as a control part arranged in the above andon the right side of these units 3, 4. These devices 3-5 constitute themain body of the projector 1.

The power supply unit 3 structurally includes a power supply 31, and alamp drive circuit (ballast), not shown, arranged beneath the powersupply 31. The power supply 31 feeds the power externally suppliedthrough a power cable, not shown, connected to the inlet connector tothe lamp drive circuit, the control board 5 and so on.

The lamp drive circuit feeds the power supplied from the power supply 31to a light source lamp, not shown in FIGS. 3 and 4, constituting theoptical unit 4, which is electrically connected to the light sourcelamp. The lamp drive circuit like this can be configured by making awiring on a board, for example.

The power supply 31 and the lamp drive circuit are arranged upper andlower nearly parallel, the occupation space of which extends in the leftand right directions at the rear of the projector 1.

Meanwhile, the power supply 31 and the lamp drive circuit are coveredover by a metal shield member 31A, such as of aluminum, opened at leftand light sides.

The shield member 31A has a function to prevent the electromagneticnoise caused on the power supply 31 and lamp drive circuit from leakingto the outside, in addition to a function as a duct to induce coolingair.

The control board 5 has, as shown in FIG. 3, a main board 51 arrangedcovering over the units 3, 4 and including a CPU, a connection 51B, etc.and an interface board 52 arranged underneath the main board 51 andincluding a connection 52A.

In the control board 5, the CPU, etc. of the main board 51 control aliquid-crystal panel constituting an optical device, referred later,according to the image information inputted through the connections 51B,52A.

The main board 51 is covered over by a metal shield member 51 a. Themain board 51 is in abutment against an upper end 472A (FIG. 4) of anupper light guide 472 constituting the optical unit 4 although not easyto see in FIG. 3.

Here, FIG. 5 is an exploded perspective view showing the optical unit 4.FIG. 6 is a view typically showing the optical unit 4.

The optical unit 4 is a unit for optically processing a luminous fluxemitted from a light-source lamp 416 structuring the light-source device411 and forming an optical image corresponding to image information,thereby projecting the optical image by magnification, as shown in FIG.6. This has an integrator-illuminating optical system 41,color-separating optical system 42, a relay optical system 43, anoptical device 44, a projection lens 46 and a synthetic resin lightguide 47 (FIG. 5) accommodating these optical components 41-44, 46. Thelight guide 47 is structured, as shown in FIG. 5, having a lower lightguide 471 formed with a groove for slidably fitting, from above, opticalcomponents 412-415, 418, 421-423, 431-434, 442, and an upper light guide472 in a lid form for covering the upper opening of the lower guide 471.

The integrator-illuminating optical system 41 is an optical system forilluminating nearly uniform the image regions of three liquid-crystalpanels 441 (liquid-crystal panels 441R, 441G and 441B assumably forrespective colors of red, green and blue) constituting the opticaldevice 44. This has a light-source device 411, a first lens array 412, asecond lens array 413, a polarization converter element 414 and asuperimposer lens 415.

The light-source device 411, has a light-source lamp 416 as a radiationlight source and a reflector 417, to reflect a radiation rays of lightprojected from the light-source lamp 416 upon a reflector 417 into acollimated rays of light and to project the collimated rays of light tothe outside. The light-source lamp 416 employs a high-pressure mercurylamp. Incidentally, a metal halide lamp, a halogen lamp or the like canbe adopted besides the high-pressure mercury lamp. Meanwhile, thereflector 417 employs a parabolic mirror. Incidentally, a combination ofa collimated concave lens and an elliptic mirror may be employed inplace of the parabolic mirror.

The first lens array 412 has a structure arranged, in a matrix form,with small lenses having a contour nearly rectangular as viewed in anoptical axis direction. Each small lens splits a luminous flux emittedfrom the light source lamp 416 into a plurality of partial luminousfluxes. Each small lens has a contour set to take an analogous form witha form of the image region of the liquid-crystal panel 441. For example,where the image region of the liquid-crystal panel 441 has an aspectratio (horizontal-to-vertical size ratio) of 4:3, each small lens is setat an aspect ratio of 4:3.

The second lens array 413 has a structure nearly similar to the firstlens array 412, i.e. a structure having small lenses arranged in amatrix form. The second lens array 413 has a function to focus images ofthe small lenses of the first lens array 412 onto the liquid-crystalpanel 441, together with the superimposer lens 415.

The polarization converter element 414 is arranged between the secondlens array 413 and the superimposer lens 415. The polarization converterelement 414 is to convert the light from the second lens array 413 intoone sort of polarization light. This enhances the light utilizationefficiency on the optical device 44.

Specifically, the portions of light, converted into one sort ofpolarization light by the polarization converter element 414, arefinally superimposed on the liquid-crystal panel 441 of the opticaldevice 44 by the superimposer lens 415. Because the projector 1 usingthe liquid-crystal panel 441 of a type for modulating polarization lightcan utilize only one sort of polarization light, it does not utilizenearly a half of a luminous flux from the light-source lamp 416 issuingother sorts of random polarization light. For this reason, the use ofthe polarization converter element 414 converts every luminous fluxemitted from the light-source lamp 416 into one sort of polarizationlight, thus enhancing the light utilization efficiency on the opticaldevice 44. Incidentally, such a polarization converter element 414 isintroduced in JP-A-8-304739, for example.

The color-separating optical system 42 has two dichroic mirrors 421, 422and a reflecting mirror 423, and has a function that the dichroicmirrors 421, 422 separate a plurality of partial luminous fluxes exitedfrom the integrator-illuminating optical system 41 into three colors oflight of red (R), green (G) and blue (B).

The relay optical system 43 has an incident lens 431, a relay lens 433,reflecting mirrors 432, 434, and has a function to guide to theliquid-crystal panel 441R the red color of light as a color separatedthrough the color-separating optical system 42.

On this occasion, the dichroic mirror 421 of the color-separatingoptical system 42 transmits red and green components of light of theluminous flux exited from the integrator-illuminating optical system 41,and reflects a blue component of light. The blue portion of lightreflected by the dichroic mirror 421 is reflected upon the reflectingmirror 423, to reach a blue liquid-crystal panel 441B through a fieldlens 418. The field lens 418 converts each partial luminous flux exitedfrom the second lens array 413 into a collimated luminous flux withrespect to the axis (main beam of light) thereof. This is true for thefield lens 418 provided on the liquid-crystal panel 441G, 441R at itslight incident side.

Meanwhile, of the red and green of light transmitted the dichroic mirror421, the green of light is reflected by the dichroic mirror 422 to reacha green liquid-crystal panel 441G through the field lens 418. On theother hand, the red of light transmits the dichroic mirror 422 andtravels through the relay optical system 43 and further the field lens418, thus reaching a red liquid-crystal panel 441R.

Incidentally, the reason of using the relay optical system 43 for redlight is to prevent the utilization efficiency of light from loweringdue to light scatter, etc. because red light has a optical path longerthan the optical paths of other color of light. Namely, this is to allowthe partial luminous flux entered the incident lens 431 to be conveyedto the field lens 418. Incidentally, although the relay optical system43 is structured to pass red light of the three colors of light, this isnot limitative, e.g., it may be structured to pass blue light.

The optical device 44 forms a color image from an entered luminous flux,demodulated according to image information. This has three incidentpolarizer plates 442 for the colors of light separated by thecolor-separating optical system 42 to enter, liquid-crystal panels 441R,441G, 441B as light modulators arranged in rear stages to the incidentpolarizer plates 442, an exit polarizer plate 443 arranged in a rearstage to the liquid-crystal panels 441R, 441G, 441B, and cross dichroicprism 444 as a color-synthesizing optical system.

The liquid panels 441R, 441G, 441B use, for example, poly-silicon TFTsas switch elements.

In the optical device 44, the colors of light separated by thecolor-separating optical system 42 are modulated according to imageinformation by the three liquid-crystal panels 441R, 441G, 441B, theincident polarizer plate 442 and the exit polarizer plate 443, to forman optical image.

The incident polarizer plate 442 transmits only the polarization lightin a given direction among the colors of light separated by thecolor-separating optical system 42, and absorbs the other luminous flux.This is of a substrate such as of sapphire glass bonded with apolarization film. Meanwhile, the polarizer film may be bonded on thefield lens 418 instead of using a substrate.

The exit polarizer plate 443 is structured nearly similar to theincident polarizer plate 442. This allows to transmit only thepolarization light in a given direction among the luminous flux exitedfrom the liquid-crystal panel 441 (441R, 441G, 441B), and absorbs theother luminous flux. Meanwhile, the polarizer film may be bonded on thecross dichroic prism 444 instead of using a substrate.

The incident polarizer plate 442 and the exit polarizer plate 443 areset up such that the polarization axes are orthogonal to each other.

The cross dichroic prism 444 synthesizes together the optical imagesexited from the exit polarizer plate 443 and modulated based on eachcolor, thus forming a color image. In the cross dichroic prism 444, adielectric multiplayer film for reflecting red light and a dielectricmultiplayer film for reflecting blue light are provided nearly X-formalong the interfaces of four rectangular prisms. By these dielectricmultilayer films, three colors of light are synthesized together. Thecross dichroic prism 444 like this is structured of optical glass.

The projection lens 46 magnifies and projects the color imagesynthesized by the cross dichroic prism 444 of the optical device 44.

The liquid-crystal panel 441, exit polarizer plate 443 and crossdichroic prism 444 explained so far are integrated into a unitstructured as an optical device main body 45. FIG. 7 is a perspectiveview showing the optical device main body 45 while FIG. 8 is an explodedperspective view showing the optical device main body 45.

The optical device main body 45 has, as shown in FIGS. 7 and 8, a crossdichroic prism 444, a pedestal 447 fixed at an underside of the crossdichroic prism 444, a metal fixing plate 446 attached at a luminous-fluxincident end face of the cross dichroic prism 444 and holding the exitpolarizer plate 443, and a liquid-crystal panel 441 (441R, 441G, 441B)fixed at the luminous-flux incident side of the fixing plate 446 by fourmetal screws 446P.

The pedestal 447 is structured of magnesium alloy for example, the outerperipheral shape of which is nearly same as the cross dichroic prism444.

The fixing plate 446 is attached on a luminous-flux exit side of theliquid-crystal panels 441R, 441G, 441B, to fix the liquid-crystal panels441R, 441G, 441B at the luminous-flux incident end face of the crossdichroic prism 444 and to sustain the exit polarizer plate 443. Thefixing plate 446 has an expansion coefficient of preferably 7.0×10⁻⁶ orgreater and 26×10⁻⁶ or smaller. Particularly, it is preferably at oraround an intermediate value in expansion coefficient of the crossdichroic prism 444 and a holder frame 8, referred later. In thisembodiment, the fixing plate 446 of iron has an expansion coefficient of1.2×10⁻⁶. This fixing plate 446 has a plate part 446A generallyrectangular in plan formed with an opening 446A1 at the center, and legparts 446B formed at four corners of the plate part 446A.

The plate part 446A is made in a shape to be received in theluminous-flux incident end face of the cross dichroic prism 444.Meanwhile, the opening 446A1 of the plate part 446A is formedcorresponding to the image region of the liquid-crystal panel 441. Ineach of four sides of a luminous-flux exit surface of the plate part446, there are alternately formed a first cutout 446A3 extending fromthe opening 446A1 toward the outer edge of the plate part 446A andgenerally orthogonal to a lengthwise direction of each side, and asecond cutout 446A4 extending from the outer edge toward the opening446A1 and generally orthogonal to a lengthwise direction of each side.The first cutouts 446A43 are formed one on each side (totally four)while the second cutouts 446A4 are formed two on each side (totallyeight). Accordingly, the cutouts 446A3, 446A4 are totally 12 in thenumber.

The number of the first cutouts 446A3 and second cutouts 446A4 is thevalue resulting when the expansion coefficient of the fixing plate 446is divided by the expansion coefficient of the cross dichroic prism 444,is rounded up in its decimal part into an integer, and then ismultiplied by an integer. Namely, in this embodiment, the cross dichroicprism 444 is made of optical glass and has an expansion coefficient of7.6×10⁻⁶ while the fixing plate 446 is made of iron and has an expansioncoefficient of 11.2×10⁻⁶. Accordingly, the value the expansioncoefficient of the fixing plate 446 is divided by the expansioncoefficient of the cross dichroic prism 444 is 1.5. This, if made to aninteger, gives a value 2. Accordingly, the number of the cutouts 446A3and cutouts 446A4 is 12 that is given by 2 times 6.

Furthermore, the plate part 446A is formed with a hole 446Acorresponding to a hole in a holder frame 8, referred later. The hole446A5 and the hole 821 of the holder frame 8 are fixed together byscrews 446P. This attaches the liquid-crystal panel 441 on the fixingplate 446,

The leg part 446B has a fixing part 446B1 to be firmly fixed to thecross dichroic prism 444 and a connecting section 446B2 for connectingthe fixing part 446B1 with the plate part 446A. The fixing parts 446B1are soldered onto the metal layers 444A attached at the four corners ofthe cross dichroic prism 444. The connecting part 446B2 has a sectionalarea smaller than the planer area of the fixing part 446B1 so that theconnecting part 446B2 can absorb a force caused due to a difference inexpansion coefficient between the fixing plate 446 and the crossdichroic prism 444. The leg parts 446B may be integrally formed on theplate part 446A or separate members therefrom.

Meanwhile, the liquid-crystal panel 441, as shown in FIG. 8, isstructured having a liquid-crystal panel main body (light modulatorelement) 441X generally rectangular in plan, anti-dust glass 441D, 441Cclosely bonded on the liquid-crystal panel main body 441X at itsluminous-flux incident and exit sides, a holder 7 accommodating andholding therein the liquid-crystal panel main body 441X and anti-dustglass 441D, 441C.

The liquid-crystal panel main body 441X has a liquid crystal (lightmodulator proper) filled between a drive substrate (e.g. substrateformed with a plurality of line-formed electrodes, electrodesconfiguring pixels, TFT elements electrically connected between those)441A and a counter substrate (e.g. substrate formed with a commonelectrode), thus having a structure that a control cable 441F extendsbetween these substrates.

The liquid-crystal panel main body 441X has a diagonal dimension of theimage region of 0.7 inches, for example.

The material structuring the drive substrate 441A and counter substrate441E is preferably a material having a heat conductivity of 1 W/m·K orgreater, e.g., quartz.

The anti-dust glass 441C, 441D are respectively secured on the drivesubstrate 441A and the counter substrate 441E by transparent adhesive orthe like.

Those anti-dust glass 441C, 441D optically makes inconspicuous the dustadhered on a panel surface by deviating the panel surface position ofthe liquid panel 441 from a back focus position of the projection lens46.

The material of structuring the anti-dust glass 441C, 441D is preferablya material having a conductivity of 1 W/m·K or greater, e.g., quartz.

Incidentally, although this embodiment used quartz or the like as amaterial of the drive substrate 441A, counter substrate 441E and theanti-dust glass 441C, 441D, this is not limitative, e.g., sapphire, rockcrystal, flour and the like are usable.

The holder 7 has a holder frame 8 accommodating and sustaining theliquid-crystal panel main body 441X and the anti-dust glass 441C, 441D,and a frame-like member 9 for fixing under pressure the accommodatedliquid-crystal panel main body 441X and anti-dust glass 441C, 441D.

The frame-like member 9 has an opening 91 for luminous-flux transmissionin a rectangular form provided in a position corresponding to the imageregion of the liquid-crystal panel main body 441X. Meanwhile, hooks 92are provided respectively at left and right of the frame-like member 9.By engaging the hooks 92 with hook engaging parts 832 referred later,the holder frame 8 and the frame-like member 9 are fixed together.

Next, the holder frame 8 is explained with reference to FIGS. 10 to 17.The holder frame 8 is a member generally rectangular in plan having asize corresponding to the liquid-crystal panel main body 441X having adiagonal of its image region of 0.7 inch. The holder frame 8 isstructured of a material having an expansion coefficient of 7.0×10⁻⁶ orgreater and 26×10⁻⁶ or smaller and a heat conductivity of 10 W/m·K orgreater. Such materials include MG alloy, for example.

Incidentally, although this embodiment exemplified Mg alloy as amaterial of the holder frame 8, it should be understood that this is notlimiting, i.e., Al alloy, Mo—Cu alloy, Ti alloy, Fe—Ni alloy and thelike are usable.

An opening 81 for luminous-flux transmission in a rectangular form isprovided in the holder frame 8 in a position corresponding to the imageregion of the liquid-crystal panel main body 441X, as shown in FIG. 10.

Meanwhile, quadrangular-prism fixing parts 82 are formed at four cornersof the holder frame 8. The fixing part 82 is formed with a hole 821.Here, it is assumed that a pair of longer sides of the holder frame 8are longer sides 8A, 8D while a pair of shorter sides are shorter sides8B, 8C.

As shown in FIG. 11, the holder frame 8 has a first accommodating part83 accommodating the anti-dust glass 441C and the drive substrate 441A,and second accommodating part 84 accommodating the anti-dust glass 441Dand the counter substrate 441E.

The first accommodating part 83 has a first outer peripheral wall 831for holding the side surface of the anti-dust glass 441C and drivesubstrate 441A. The first outer peripheral wall 831, configuring theshorter sides 8C, 8B and the longer side 8A of the holder frame 8, has apair of shorter sides 831B, 831C and a longer side 831A, thus being madegenerally in a squared-U form in plan opened at the side opposite to thelonger side 831A. Although the first outer peripheral wall 831 connectsa fixing part 82, a flat-plate part 85 is arranged between two fixingparts 82 not connected by the first outer peripheral wall 831 (betweentwo fixing parts 82 arranged on the opening side opposite to the longerside 831A of the first outer peripheral wall 831). The flat-plate part85 extends nearly parallel with a luminous-flux incident surface of theanti-dust glass 441C and drive substrate 441A accommodated in the firstaccommodating part 83. The control cable 441F mentioned before is laidon the flat-plate part 85.

On an accommodating surface (surface close to the anti-dust glass 441Cand drive substrate 441A) of the first outer peripheral wall 831, thereis formed a positioning projection 831D for positioning the anti-dustglass 441C and drive substrate 441A.

Meanwhile, hook engaging parts 832 are formed on the outer surfaces ofthe one pair of shorter sides 831B, 831C of the first outer peripheralwall 831 (back surfaces to the accommodating surfaces close to theanti-dust glass 441C and drive substrate 441A) in positionscorresponding to the hooks 92 of the foregoing frame-like member 9.

A second accommodating section 84 has an outer diameter smaller than theouter diameter of the first accommodating section 83, to project towardthe luminous-flux incident side with respect to the first accommodatingsection 83. The second accommodating section 84 has a second outerperipheral wall 841 for holding the side surface of the anti-dust glass441D and counter substrate 441E, and a fixing wall 842 for fixing theanti-dust glass 441D at its outer periphery of luminous-flux incidentsurface.

The second outer peripheral wall 841 is generally rectangular in plan,and has a pair of shorter sides 841B, 841C configuring the shorter sides8B, 8C of the holder frame 8, and a pair of longer sides 841A, 841Dconfiguring the longer sides 8A, 8D of the holder frame 8.

On an accommodating surface (surface close to the anti-dust glass 441Dand drive substrate 441E) of the second outer peripheral wall 841, thereis formed a positioning projection 841E for positioning the anti-dustglass 441D and counter substrate 441E. Meanwhile, between the shorterside 841B of the second outer peripheral wall 841 and the shorter side8311B of the first outer peripheral wall 831 and between the shorterside 841C of the second outer peripheral wall and the shorter side 831Cof the first outer peripheral wall 831, there are provided connectionwalls 86 connecting these shorter sides together. The connection wall 86is generally orthogonal to the shorter side 841B, 841C of the secondouter peripheral wall 841 and to the shorter side 831B, 831C of thefirst outer peripheral wall 831.

Incidentally, no connection wall is provided between the longer side841A of the second outer peripheral wall 841 and the longer side 831A ofthe first outer peripheral wall 831.

As shown in FIG. 10, on the luminous-flux incident surface of theconnection wall 86 and in the vicinity of the fixing part 82 connectedby the flat-plate part 85, a convex T is formed bestriding aluminous-flux incident surface of the connecting wall 86 and aluminous-flux incident surface of the second outer peripheral wall 841and the fixing wall 842 of the second accommodating part 84.

Meanwhile, as shown in FIG. 11, the second outer peripheral wall 841 hasan end face close to the first outer peripheral wall 831 projectingtoward the first outer peripheral wall 831 with respect to theconnection wall 86 and abutting against the outer periphery on theluminous-flux incident surface of the drive substrate 441A accommodatedin the first accommodating part 83.

The fixing wall 842 is provided at a side opposite to the first outerperipheral wall 831 with respect to the second outer peripheral wall 841in a manner nearly orthogonal to the second outer peripheral wall 841,to abut against the luminous-flux incident surface of the anti-dustglass 441D. This fixing wall 842 is formed with the foregoing opening 81in the center thereof. The fixing wall 842 has a pair of longer sides842A, 842D and a pair of shorter sides 842B, 842C.

In the four sides of the luminous-flux incident surface of the holderframe 8, there are formed a plurality of cutouts 87A-87L extending froma vicinity of the opening 81 toward the outer edge of the luminous-fluxincident surface and nearly orthogonal to the longitudinal direction ofeach side. These cutouts 87A-87L are formed by being cut out in a mannerbeing dented in the luminous-flux incident surface toward theaccommodating surface in the backside (flat-plate part 85 is on the sidethe control cable 441F of the liquid-crystal panel main body 441×isprovided). In this embodiment, cutouts are formed, e.g. three, in eachside of the luminous-flux incident surface of the holder frame 8, whichare twelve in the total number.

The cutouts 87A, 87C are respectively formed in the longitudinal ends ofthe longer side 8D of the holder frame 8. The cutout 87A, 87C extendsfrom the longer side 842D of the fixing wall 842 to a vicinity of thehole 821 of the fixing part 82 through the longer side 841D of thesecond outer peripheral wall 841.

The cutout 87B is formed in the longer side 8D of the holder frame 8nearly at a longitudinal center thereof. The cutout 87B extends from thelonger side 842D of the fixing wall 842 to a vicinity of the outer edgeof the flat-plate part 85 through the longer side 841D of the secondouter peripheral wall 841, as also shown in FIG. 13. Incidentally, FIG.13 is a sectional view taken along the cutout 87B of the holder frame 8,which is a sectional view in the direction XIII-XIII in FIG. 12.

The cutout 87D is formed in one end of the shorter side 8B of the holderframe 8. This is made by cutting the convex T out of the shorter side842B of the fixing wall 842, to extend to the connection wall 86.

Furthermore, the cutout 87E is formed in the shorter side 8B of theholder frame 8 nearly at a longitudinal center thereof. This is made bycutting out the shorter side 842B of the fixing wall 842, the shorterside 841B of the second outer peripheral wall 841 and the connectionwall 86. This cutout 87E extends from a boundary between the shorterside 842B of the fixing wall 842 and the shorter side 841B of the secondouter peripheral wall 841 to a vicinity of a boundary between theconnection wall 86 and the shorter side 831B of the first outerperipheral wall 831, as also shown in FIG. 14. Incidentally, FIG. 14 isa sectional view taken along the cutout 87E of the holder frame 8, whichis a sectional view in the direction XIV-XIV in FIG. 12.

The cutout 87F is formed in the other end of the shorter side 8B of theholder frame 8 in a manner orthogonal to a lengthwise of the shorterside 8B. This is made by cutting from a boundary between the shorterside 842B of the fixing wall 842 and the shorter side 841B of the secondouter peripheral wall 841 to a boundary between the connection wall 86and the shorter side 831B of the first outer peripheral wall 831.

Furthermore, the cutout 87G and the cutout 871 are respectively formedin the ends of the longer sides 8D of the holder frame 8. This extendsfrom the longer side 842A of the fixing wall 842 to a vicinity of thehole 821 in the fixing part 82 through the longer side 841A of thesecond outer peripheral wall 841.

The cutout 87H is formed nearly in the center of the longer side 8D ofthe holder frame 8. This is made by cutting out the longer side 842A ofthe fixing wall 842 and the longer side 841A of the second outerperipheral wall 841.

The cutouts 87J-87L are formed in the shorter side 8C of the holderframe 8, which are respectively formed substantially similarly to theopposite cutouts 87F-87D with respect to the opening 81.

Meanwhile, in the four sides of the accommodating surface accommodatingthe anti-dust glass 441C, drive substrate 441A, anti-dust glass 441D andcounter substrate 441, a plurality of cutouts 88A-88H are formedextending from a vicinity of the opening 81 toward the outer edge of theaccommodating surface and generally orthogonal to the lengthwise of eachside, as shown in FIGS. 11 and 15. These cutouts 88A-88H are formed bybeing cut out in a manner dented in the accommodating surface toward theluminous-flux incident surface of the backside.

In this embodiment, two cutouts are formed in each side of theaccommodating surface, which are eight in the total number, for example.The cutouts in each side of the accommodating surface of the holderframe 8 are formed in positions between the cutouts formed in each sideof the luminous-flux incident surface of the holder frame 8 as viewedfrom the side of luminous-flux incidence. Namely, in each side of theholder frame 8, alternately arranged are the cutouts formed in theaccommodating surface and the cutouts formed in the luminous-fluxincident surface.

The cutout 88A is formed in a vicinity of one end lengthwise of thelonger side 8D of the holder frame 8, to position between the cutout 87Aand the cutout 87B. The cutout 88B is formed in a vicinity of the otherend lengthwise of the longer side 8D of the holder frame 8, to positionbetween the cutout 87B and the cutout 87C. These cutouts 88A and 88Bextend from the longer side 841D of the second outer peripheral wall 841to a vicinity of the flat-plate part 85, as also shown in FIG. 16. FIG.16 is a sectional view in a direction XVI-XVI in FIG. 15.

The cutout 88C is formed in a vicinity of one end lengthwise of theshorter side 8B of the holder frame 8, to position between the cutout87D and the cutout 87E. The cutout 88D is formed in a vicinity of theother end lengthwise of the shorter side 8B of the holder frame 8, toposition between the cutout 87E and the cutout 87F. These cutouts 88C,88D extend from a vicinity of the connection wall 86 of the shorter side841B of the second outer peripheral wall 841 to the first outerperipheral wall 831 through the connection wall 86.

The cutout 88E is formed in a vicinity of one end lengthwise of thelonger side 8A of the holder frame 8, to position between the cutout 87Gand the cutout 87H. The cutout 88F is formed in a vicinity of the otherend lengthwise of the longer side 8A of the holder frame 8, to positionbetween the cutout 87H and the cutout 87I. These cutouts 88E, 88F extendfrom the longer side 841A close to the fixing wall of the second outerperipheral wall 841 toward the longer side 831A of the first outerperipheral wall 831.

Incidentally, the first outer peripheral wall 831 is not cut by thecutouts 88E and 88F.

The cutout 88G is formed in a vicinity of one end lengthwise of theshorter side 8C of the holder frame 8, to position between the cutout87J and the cutout 87K. The cutout 88H is formed in a vicinity of theother end lengthwise of the shorter side 8C of the holder frame 8, toposition between the cutout 87K and the cutout 87L. These cutouts 88G,88H extend from a vicinity of the connection wall 86 of the shorter side841C of the second outer peripheral wall 841 to the first outerperipheral wall 831 through the connection wall 86, as also shown inFIG. 17. FIG. 17 is a sectional view in a direction XVII-XVII in FIG.15.

The number of the cutouts formed in each side of the holder frame 8 canbe determined in the following manner.

Provided that the exterior air of the holder frame 8 has a temperaturechange T, the holder frame 8 has an expansion coefficient α1, thesubstrate 441A, 441E has an expansion coefficient α2, the gap previouslyset between the accommodating surface of the holder frame 8 and thesubstrate 441A, 441E has a dimension X and the accommodating surface ofthe holder frame 8 has a one-side length L, then the number of cutoutsto be formed in one side of the accommodating surface and luminous-fluxincident surface is given as the number greater than the value which iscalculated by {T(α1−α2)L}/X and then is changed to an integer value. Forexample, when the exterior air temperature of the holder frame 8 changesfrom 25° C. to −20° C., T=45 results. Meanwhile, in this embodiment,because the holder frame 8 is made of Mg alloy, the holder frame 8 hasan expansion coefficient α1=26×10⁻6. Furthermore, in this embodiment,because the substrate 441A, 441E is of quartz, the expansion coefficientα2 is 0.58×10⁻⁶. Meanwhile, provided that the gap X has a dimension 0.01mm, the longer side of the accommodating surface has a length 18.1 mmand the shorter side has a length 14.7 mm, then {T(α1−α2)L}/X=2.1 or 1.7results. Accordingly, in case these values are rounded at decimal part,the number of the cutouts to be formed in each side of the holder frame8 is determined two or more. Therefore, this embodiment forms twocutouts in each side of the accommodating surface and three in each sideof the luminous-flux incident surface.

Therefore, the present embodiment is capable of offering the followingeffects.

Usually, when the holder frame 8 contracts, a contraction force takesplace in a lengthwise direction of each side of the holder frame 8. Inthe accommodating surface and luminous-flux incident surface of theholder frame 8, because cutouts 87A-87L and cutouts 88A-88H are formedextending from a vicinity of the opening 81 toward the outer edge andorthogonal to a lengthwise direction of each side, the contracting forceof the holder frame 8 can be weakened. This can relax the force of theholder frame 8 compressing the outer periphery of the liquid-panel mainbody 441X and anti-dust glass 441C, 441D. Accordingly, the gap betweenthe substrates 441A, 441E can be kept at a predetermined dimension. Itis possible to prevent against a transmittance change in a transmittingluminous flux as caused by a gap change between the substrates 441A,441E, and a color unevenness resulting from the transmittance change.

Meanwhile, by forming the cutouts 87A-87L and cutouts 88A-88H in theholder frame 8, the substrates 441A, 441E can be prevented from beingcompressed by the holder frame 8. Accordingly, there is no need toincrease the gap between the holder frame 8 and the substrate 441A,441E. Consequently, the substrates 441A, 441E can be prevented fromdeviating in position within the holder frame 8. Furthermore, pixeldeviation can also be prevented from occurring due to positionaldeviation of the substrates 441A, 441E.

Furthermore, because of no need of securing a gap great between theholder frame 8 and the substrate 441A, 441E, light can also be preventedfrom leaking through between the holder frame 8 and the substrate 441A,441E.

In this embodiment, because the cutouts 87A-87L and cutouts 88A-88H areformed respectively in the four sides of the holder frame 8, it ispossible to positively reduce the force compressing the substrate 441A,441E upon contraction of the holder frame 8.

Furthermore, by respectively forming cutouts 87A-87L and cutouts 88A-88Hin the four sides of the holder frame 8, it is possible to positivelyprevent an occurrence of warp or strain upon contraction of the holderframe 8. Particularly, this embodiment alternately arranges the cutouts87A-87L formed in the luminous-flux incident surface of the holder frame8 and the cutouts 88A-88H formed in the accommodating surface. Becausethere is no possibility of overlap of the cutouts formed in theaccommodating surface and luminous-flux incident surface, thereencounters no extreme reduction of strength in the region where thecutout is formed. This can more positively prevent a warp or strain fromoccurring due to a contraction of the holder frame 8.

Provided that the exterior air of the holder frame 8 has a temperaturechange T, the holder frame 8 has an expansion coefficient α1, thesubstrate 441A, 441E has an expansion coefficient α2, the gap previouslyset between the accommodating surface of the holder frame 8 and thesubstrate 441A, 441E has a dimension X and the accommodating surface ofthe holder frame 8 has a one-side length L, then the number of cutoutsto be formed in one side of the accommodating surface and luminous-fluxincident surface is given as the number equal to or greater than thevalue which is calculated by {T(α1−2)L}/X and then is changed to aninteger value. Accordingly, it is possible to reduce the differencebetween the contraction ratio of the holder frame 8 in a low temperaturestate and the contraction ratio of the substrate 441A, 441E. This canpositively prevent the substrate 441A, 441E from being compressed bycontraction of the holder frame 8. Furthermore, occurrence of colorunevenness can be prevented.

Meanwhile, of the cutouts 88A-88H formed in the accommodating surface ofthe holder frame 8, the cutouts 88A, 88B, 88E, 88F formed in the longerside 8D and longer side 8A are cut in a manner bestriding the secondouter peripheral wall 841 of the second accommodating part 84. However,the cutouts 88C, 88D, 88G, 88H formed in the shorter side 8B, 8C areformed by cutting only a part (part in a vicinity of the connection wall86) of the second outer peripheral wall 841. By thus making the cutouts88C, 88D, 88G, 88H in a structure that the second outer peripheral wall841 is cut only in a part thereof, the strength of the secondaccommodating part 84 can be secured to a predetermined value or more.

Meanwhile, in this embodiment, because the cutouts 88E, 88F formed inthe longer side 8A were made in a structure without cutting the firstouter peripheral wall 831, the strength of the first accommodating part83 can be secured to a predetermined value or more.

In this embodiment, the substrates 441A, 441E and anti-dust glass 441D,441C are structured of a material having a heat conductivity of 1 W/m·Kor greater, e.g. quartz. Accordingly, the heat caused on theliquid-crystal main body 441X is allowed to dissipate to the holderframe 8 through the substrates 441A, 441E and anti-dust glass 441D,441C. Meanwhile, by forming the substrates 441A, 441E and anti-dustglass 441D, 441C with a material having a high heat conductivity, thesubstrate 441A, 441E can be made uniform in respect of in-planetemperature distribution, preventing more positively thermal strainoccurrence and color unevenness occurrence due to such thermal strain.

Furthermore, by making the holder frame 8 of Mg alloy and providing itwith a heat conductivity as high as 10 W/m·K in heat conductivity, it ispossible to release the heat transferred from the substrate 441A, 441Eof the liquid-crystal panel main body 441X to the holder frame 8. Thismakes uniform the in-plane temperature distribution on the substrate441A, 441E, positively preventing against the heat strain caused by thesubstrate 441A, 441E.

Meanwhile, in the four sides of the luminous-flux exit surface of thefixing plate 446, because there are formed the first cutout 446A3 andthe second cutout 446A4 that extend orthogonal to the lengthwise of eachside, the fixing plate 446 can be suppressed from expanding/contracting.This can prevent the liquid-crystal panel 441 from being applied by adeforming force of expansion and contraction of the fixing plate 446.Thus, the gap between the substrates 441A, 441E of the liquid-crystalpanel 441 can be kept at a predetermined dimension. Accordingly, it ispossible to prevent a transmittance change of transmitting luminous fluxas caused by a change of the gap between the substrates 441A, 441E, andan occurrence of color unevenness due to a transmittance change.

Meanwhile, the holder frame 8 and the fixing plate 446 are fixedtogether by screws 446P. Accordingly, where there is a great differencebetween the contraction ratio of the holder frame 8 and the contractionratio of the fixing plate 446, the fixing plate 446 or the holder frame8 is possibly deformed about the screw 446P by the force resulting fromthe difference in contraction ratio. On the contrary, in thisembodiment, cutouts are formed in both the holder frame 8 and the fixingplate 446 to thereby reduce the contraction ratio of the holder frame 8as well as the contraction ratio of the fixing plate 446. Hence, it ispossible to prevent the deformation caused by a difference incontraction ratio.

Because the fixing plate 446 is formed with the first cutout 446A3 andthe second cutout 446A4, the fixing plate 446 can be suppressed fromexpanding/contracting. Thus, the expansion/contraction ratio of thefixing plate 446 can be approximated to the expansion/contraction ratioof the cross dichroic prism 444. This can reduce the force caused by adifference in expansion/contraction ratio between the fixing plate 446and the cross dichroic prism 444, making it possible to prevent apositional deviation of the fixing plate 446 relative to the crossdichroic prism 444 and further a positional deviation of theliquid-crystal panel 441 fixed on the fixing plate 446. Because of thecapability of preventing against a positional deviation of theliquid-crystal panel 441, pixel deviation can be also prevented that isto occur due to positional deviation of the liquid-crystal panel 441.

Meanwhile, in the plate part 446A of the fixing plate 446, there arealternately formed, on each side, the first cutout 446A3 extending fromthe opening 446A1 toward the outer edge and the second cutout 446A4extending from the outer edge toward the opening 446A1. Accordingly,warp can be prevented that is to occur upon expansion/contraction of thefixing plate 446.

The number of the cutouts 446A3, 446A4 is the value resulting when theexpansion coefficient of the fixing plate 446 is divided by theexpansion coefficient of the cross dichroic prism 444, is rounded up inits decimal part into an integer, and then is multiplied by an integer.By making the number of cutouts 446A3, 446A4 as the above number, it ispossible to reduce the difference between the expansion/contractionratio of the fixing plate 446 and the expansion/contraction ratio of thecross dichroic prism 444. Accordingly, it is possible to positivelyprevent a positional deviation of the fixing plate 446 relative to thecross dichroic prism 444 and furthermore a positional deviation of theliquid-crystal panel 441 fixed on the fixing plate 446. This can preventpixel deviation as caused by a positional deviation of theliquid-crystal panel 441.

Furthermore, in this embodiment, because one first cutout 446A3 isformed per side while two second cutouts 446A3 are formed per side, thestrength of the fixing plate 446 can be secured at a predetermined valueor more.

Meanwhile, in this embodiment, the expansion coefficient of the fixingplate 446 was taken as a value at or around the intermediate value ofthe expansion coefficient of the holder frame 8 and the expansioncoefficient of the cross dichroic prism 444. Accordingly, the differenceis reduced between the expansion coefficient of the holder frame 8 andthe expansion coefficient of the cross dichroic prism 444.

Namely, because of a reduced difference between the expansioncoefficient of the holder frame 8 and the expansion coefficient of thefixing plate 446, the holder frame 8 can be positively prevented frombeing applied by a force caused by expansion/contraction of the fixingplate 446, making it possible to prevent a transmittance change oftransmitting luminous flux through the liquid-crystal panel 441 andfurthermore an occurrence of color unevenness due to a transmittancechange.

Meanwhile, because of a reduced difference between the expansioncoefficient of the holder frame 8 and the expansion coefficient of thecross dichroic prism 444, it is possible to positively prevent apositional deviation of the fixing plate 446 relative to the crossdichroic prism 444 and furthermore a pixel deviation caused by thepositional deviation.

Incidentally, it should be understood that the invention is not limitedto the foregoing embodiment but the modifications, revisions, etc.within the scope the object of the invention is to be achieved areincluded in the invention.

For example, in the foregoing embodiment, although the substrates 441A,441E are made of quartz, this is not limitative. For example, thesubstrates may be structured of a material, such as sapphire, rockcrystal or the like.

Because such a material is extremely high in thermal conductivity, bystructuring a substrate of such a material, the substrate can be mademore uniform in in-plane temperature distribution, making it possible toeffectively prevent thermal strain occurrence.

Furthermore, in the foregoing embodiment, although the holder frame 8was made of Mg alloy, this is not limitative. For example, the holderframe 8 may be structured of a material, such as Mo—Cu alloy, PPS(polyphenylene sulfide), Al alloy, Fe—Ni alloy or Ti alloy.

Meanwhile, in the foregoing embodiment, the liquid-crystal panel mainbody 441X has an image region with a diagonal dimension of 0.7 inch, toadopt a holder frame 8 in a size suited for the liquid-crystal panelmain body 441X. However, this is not limitative. The image region of theliquid-crystal panel main body 441X may be in a diagonal dimension of0.5 inch, 0.9 inch or 1.3 inches. In this case, the number of cutouts tobe formed in each side of the holder frame is preferably two or more for0.5 inch, three or more for 0.9 inch, four or more for 1.3 inches, fouror more for 1.5 inches, and five or more for 1.8 inches.

Furthermore, in the foregoing embodiment, although the substrates 441A,441E and the anti-dust glass 441C, 441D were structured of the samematerial, this is not limitative, i.e., may be structured of differentmaterials. On this occasion, the holder frame 8 compresses the outerperiphery of the anti-dust glass or the substrate which is smaller incompression ratio. For example, in the case that the holder framecompresses the outer periphery of the anti-dust glass, the pair ofsubstrate is compressed through the anti-dust glass, possibly changingthe spacing between the substrates. In this case, the number of cutoutsto be formed on each side of the holder frame 8 is: provided that theexterior air of the holder frame 8 has a temperature change T, thesmaller expansion coefficient of the expansion coefficients of thesubstrate or the anti-dust glass is α3, the expansion coefficient of theholder frame is α1, the gap previously set between the accommodatingsurface of the holder frame 8 and the substrate has a dimension of X andthe accommodating surface of the holder frame 8 is a one-side length ofL, then the number is preferably given as the number greater than thevalue which is calculated by {T(α1−α3)L}/X and then is changed to aninteger value. If doing so, by forming cutouts in this number in theholder frame, it is possible to reduce the difference between thesmaller contraction ratio of the anti-dust glass and the substrate andthe contraction ratio of the holder frame. This can prevent thecompression of the substrate due to the contraction of the holder frame.

Furthermore, in the foregoing embodiment, the number of cutouts to beformed in each side of the holder frame 8 is: provided that the exteriorair of the holder frame 8 has a temperature change T, the holder frame 8has an expansion coefficient α1, the substrate 441A, 441E has anexpansion coefficient α2, the gap previously set between theaccommodating surface of the holder frame 8 and the substrate 441A, 441Eis a dimension X and the accommodating surface of the holder frame 8 hasone side length L, then the number is given as the number greater thanthe value which is calculated by {T(α1−α2)L}/X and then is changed to aninteger value. However, this is not limitative. For example, the totalnumber of cutouts to be formed in the holder frame may be given thenumber as the value resulting when the expansion coefficient of theholder frame is divided by the expansion coefficient of the substrateand then is rounded up at the decimal part into an integer. By doing so,the difference can be reduced between the expansion coefficient of theholder frame and the expansion coefficient of the substrate.

Furthermore, instead of determining the number of cutouts by the abovecalculation way, the number of cutouts may be determined by takingaccount of the strength of the holder frame 8 and the like.

Meanwhile, in the foregoing embodiment, although the cutouts 87A-87L andthe cutouts 88A-88H were formed in each side of the holder frame 8,there may be a side where cutouts are not formed.

Meanwhile, although, in the foregoing embodiment, there were alternatelyarranged, in each side, the cutouts 88A-88H formed in the accommodatingsurface and the cutouts 87A-87L formed in the luminous-flux incidentsurface, this is not limitative, i.e. may not be alternate arrangement.In doing so, because a cutout can be suitably formed, cutouts are madeeasy to form.

Furthermore, in the foregoing embodiment, although the expansioncoefficient of the fixing plate 446 was given a value at or around theintermediate value in expansion coefficient between the cross dichroicprism 444 and the holder frame 8, referred later, this value is notlimitative. Meanwhile, the expansion coefficient of the fixing plate 446may be out of the range of 7.0×10⁻⁶ or greater and 26×10⁻⁶ or smaller.

Furthermore, the number of cutouts 446A3, 446A4 was given the valueresulting when the expansion coefficient of the fixing plate 446 isdivided by the expansion coefficient of the cross dichroic prism 444,and then is changed into an integer, this is not limitative. Forexample, the number of cutouts may be determined by taking account ofthe strength of the fixing plate 446.

Meanwhile, the number of cutouts to be formed in the fixing plate 446may be the value resulting when the expansion coefficient of the holderframe 8 is divided by the expansion coefficient of the fixing plate 446,and then is rounded up in decimal part into an integer. In doing so, thedifference in expansion/contraction ratio can be reduced between theholder frame 8 and the fixing plate 446. This can prevent the holderframe 8 from being acted upon by a force resulting fromexpansion/contraction of the fixing plate 446.

Meanwhile, in the foregoing embodiment, although the cutout 446A3 andcutout 446A4 of the fixing plate 446 were alternately arranged on eachside, this is not limitative, i.e. may not be alternative arrangement.This facilitates to form cutouts.

While this invention has been described in conjunction with the specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, preferred embodiments of the invention as set forthherein are intended to be illustrative, not limiting. There are changesthat may be made without departing from the spirit and scope of theinvention.

1. A fixing plate attached at a luminous-flux exit side of a lightmodulator device that modulates a luminous flux emitted from a lightsource in accordance with image information and forming an opticalimage, and that fixes the light modulator device on a color-synthesizingoptical device that synthesizes colors of light exited from the lightmodulator device, the fixing plate comprising: a plate part in arectangular plate form fixing the light modulator device and formed withan opening that transmits a luminous flux exited from the lightmodulator device, a cutout in a groove form being formed extendingnearly orthogonal to a lengthwise of each side, in four sides of aluminous-flux incident surface or luminous-flux exit surface of theplate part.
 2. The fixing plate according to claim 1, the cutout havinga first cutout part extending from the opening toward an outer edge anda second cutout part extending from the outer edge toward the opening,the first cutout part and the second cutout part being alternatelyformed in each side.
 3. The fixing plate according to claim 1, a numberof the cutouts being the value resulting when an expansion coefficientof the fixing plate is divided by an expansion coefficient of thecolor-synthesizing optical device and then is changed into an integer,or the above value changed into an integer is multiplied by an integer.4. The fixing plate according to claim 1, the expansion coefficient is7.0×10⁻⁶ or greater and 26×10⁻⁶ or smaller.
 5. A fixing plate accordingto claim 4, the light modulator device having a light modulator elementthat modulates an incident luminous flux and a holder frame holding thelight modulator element and fixed on the fixing plate, the expansioncoefficient being a value nearly intermediate between the expansioncoefficient of the color-synthesizing optical device and an expansioncoefficient of the holder frame of the light modulator device.
 6. Anoptical device having a light modulator device that modulates a luminousflux emitted from a light source in accordance with image informationand forming an optical image, and a color-synthesizing optical devicethat synthesizes colors of light modulated by the light modulatordevice, the optical device comprising: a fixing plate that fixes thelight modulator device at a luminous-flux incident end face of acolor-synthesizing optical device, the fixing plate being a fixing plateaccording to claim
 1. 7. A projector comprising the optical deviceaccording to claim 6, and a projection optical system that projects animage formed by the optical device.